Allow the input line to be NULL, and teach strnsubst() that NULL means to use

a nil-string.

2 files changed, 8 insertions, 3 deletions

diff --git a/usr.bin/xargs/strnsubst.c b/usr.bin/xargs/strnsubst.c
index 5ca2773..b6668b7 100644
--- a/usr.bin/xargs/strnsubst.c
+++ b/usr.bin/xargs/strnsubst.c
@@ -24,6 +24,8 @@ void	strnsubst(char **, const char *, const char *, size_t);
  * maxsize bytes large.  It does not free the string pointed to by str, it
  * is up to the calling program to be sure that the original contents of
  * str as well as the new contents are handled in an appropriate manner.
+ * If replstr is NULL, then that internally is changed to a nil-string, so
+ * that we can still pretend to do somewhat meaningful substitution.
  * No value is returned.
  */
 void
@@ -38,6 +40,9 @@ strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
 	if (s2 == NULL)
 		err(1, "calloc");
 
+	if (replstr == NULL)
+		replstr = "";
+
 	if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
 		strlcpy(s2, s1, maxsize);
 		goto done;
diff --git a/usr.bin/xargs/xargs.c b/usr.bin/xargs/xargs.c
index e37a7e4..832e999 100644
--- a/usr.bin/xargs/xargs.c
+++ b/usr.bin/xargs/xargs.c
@@ -454,10 +454,10 @@ prerun(int argc, char **argv)
 	free(tmp2);
 
 	/*
-	 * Free the input line buffer, and create a new dummy.
+	 * Free the input line buffer, if we have one.
 	 */
-	free(inpline);
-	inpline = strdup("");
+	if (inpline != NULL)
+		free(inpline);
 }
 
 static void